Main belt asteroids

The main asteroid belt is a region between the orbits of Mars and Jupiter that is occupied by numerous small objects. The largest asteroid, Ceres, is classified as a dwarf planet, and comprises around 30% of the mass of the entire asteroid belt. However, Ceres is much smaller than our Moon. In fact, even if all of the asteroids were combined, the resulting object would still be smaller than the Moon, and at the scale of this diagram, less than a millimeter in diameter.​About 93% of the main belt asteroids orbit within a ring that is approximately 120 feet wide at the scale of this diagram; so in relation to Ceres, the innermost asteroids are around 70 feet closer to the Sun, while the outermost asteroids are about 50 feet more distant. Light from the Sun takes about 17 minutes to reach the inner asteroids, and about 27 minutes to reach the outer belt. Here the orbits of the four largest asteroids are shown at their average distance from the Sun. Even though they are almost invisible at the scale of this model, the combined mass of Ceres, Vesta, Pallas, and Hygiea accounts for about half the mass of the entire asteroid belt.

Of these, only Ceres and Vesta have been explored at close range. On Vesta, a huge crater called Rheasilvia has a central peak that is thought to be the highest mountain in our Solar System: it rises about 14 miles above the crater floor. (This is over twice as high as the closest rival on Earth: the island of Hawaii rises about 6 miles from its base on the sea floor to the summit of Mauna Kea. In comparison, Mt. Everest rises about 2.5 miles above the surrounding terrain.)

You can view these links to learn more about Ceres and the asteroid belt: